About 150 people have fallen ill aboard a cruise ship berthed in Scotland following a suspected outbreak of the vomit-inducing norovirus, health officials said Monday.

A 74-year-old English man has also died on board the Marco Polo, which is berthed near Invergordon in northeastern Scotland, but the ship's operators said his death was unrelated to the outbreak.

Two people have been hospitalised and the others are being treated on board, according to Ken Oates, the local National Health Service (NHS) director of public health.

"NHS Highland can confirm that around 150 people on board a cruise ship docked at Invergordon have become unwell with suspected norovirus," he said.

"The Marco Polo docked today. This evening two people have been admitted to Raigmore Hospital who are showing symptoms of norovirus."

Germany-based operators Transocean Tours said the man's death earlier Monday was unrelated to the outbreak, saying he had chronic heart and breathing problems and "suffered a fatal heart attack on board ship".

It said 769 passengers and 340 crew were on the Marco Polo and its medical team had reported that 54 passengers and 21 crew "have an unconfirmed virus that causes a form of gastroenteritis".

Norovirus is highly contagious and induces vomiting and diarrhea. It affects between 600,000 and one million people in Britain each year and outbreaks are common within contained environments.

Passengers on the world-famous Queen Elizabeth II luxury liner were struck by an outbreak in 2007.